Judging a book by its cover is rightly frowned upon, but you can sure tell a lot about a string quartet by their given name. If you’d expect the Ligeti Quartet to observe a different world view from the Amadeus Quartet, then ‘Quatuor Diotima’ feels like a determined statement of intent from a young Paris-based group who hear possible futures for the string quartet emerging out of German Romanticism. Friedrich Hölderlin’s poem Hyperion co-opted the character Diotima from Plato’s Symposium, and Luigi Nono’s 1980 quartet Fragmente – Stille, an Diotima embedded quotes from Hölderlin into a score that floated the light-touch textures of Anton Webern’s pellucid late-period string quartets towards a music which hovered on the very brink of not being there. Quatuor Diotima have previously recorded modern composition ranging from Reich and Crumb to Lachenmann, Nono and Dieter Schnebel; but the complete string quartet music of Schoenberg, Webern and Berg clearly connects the Diotimas with some core concerns – who they are as musicians and from where those instincts might spring.

A disc’s worth of this material has been available before. In 2011, the Diotimas released Schoenberg’s String Quartet No 2 (with soprano Sandrine Piau) in a set alongside Berg’s Lyric Suite and Webern’s Six Bagatelles, Op 9, their performance of the Berg incorporating the recently discovered vocal version of the last movement, while their Webern presented a whole new seventh bagatelle (with voice) which the composer withdrew, fearing it wasn’t up to spec (he was wrong). The triumvirate of Schoenberg, Webern and Berg has proved the steadfast yardstick by which later cycles of quartets by the likes of Carter, Ferneyhough and Dillon have been measured; and with Schoenberg’s psychoactive String Quartet No 1 and his more emotionally measured Third and Fourth Quartets and the complete quartet music of Webern and Berg now included, a whole bunch of questions emerges about what this body of work represents and how it could be interpreted.

Quatuor Diotima couldn’t play an affected, emotionally over-ripened note if they tried. Their vision of Second Viennese School aesthetics views the backdrop of Romanticism – Brahms, Wagner, Mahler et al – as a starting-shot rather than a point of reference to be dwelt over too obsessively. When the LaSalle Quartet recorded their cycle back in the 1970s, their position as the house-string quartet of European modernism, the group with whom Ligeti worked and who cut the premiere recording of Nono’s Fragmente – Stille bled into their approach, to Webern especially. Then fast forward 10 years and the Arditti Quartet kill the emotionally volatile expressionism of Schoenberg stone dead, their clinical micromanagement dating very badly.

All of which opens up an interpretative vacuum that Quatuor Diotima eagerly fill. The opening disc featuring Schoenberg’s string quartet juvenilia – especially his String Quartet in D major, which pitches up somewhere between Schumann and Dvořák, and the equivalent moment in Webern’s development, including his Langsamer Satz and 1905 String Quartet – are absolutely not treated as mere staging posts towards mature masterworks. Listening to their articulate reading of Webern’s transitionary Five Movements, Op 5, filled me with renewed wonder: for the piece itself, yes, but also at the thought that a lesser composer kissed with the spirit of Romanticism might have been tempted to expand towards an ever-larger canvas. But, at the very moment Webern is presenting material in the opening movement, he compacts it to the point where basic sonata form is always about to fracture. An abstracted torso survives. And never have I heard that conceptual oxymoron expressed so tellingly.

That opening disc of early Schoenberg serves up a tasty enough entrée, but the set fully comes to life with the account of his First String Quartet. I know what the history books say – that, following Verklärte Nacht (1899), Schoenberg’s String Quartet No 1 (1905) represents his first fully fledged proto-modernist work. Until now I didn’t fully believe it; but Quatuor Diotima demand a rethink. As the residue of Wagnerian Romanticism is driven head first into expressionistic urgency, a flexible ribbon of unfolding structure struggles to contain its nervous impulses. The Second Quartet deftly runs towards Schoenberg’s ultimate break with tonality almost casually; the Third and Fourth Quartets, about which even hardcore Schoenbergians can blow hot and cold, are elevated beyond the arid note-picking that one too often hears. Has anyone ever unearthed such soulful splendour in the Largo from String Quartet No 4?

A plain Berg String Quartet, Op 3, is a slight weak link, perhaps; but their Lyric Suite is another performance that obliges you to reassess something entirely familiar. An almost implausible attention to shifting nuances of timbre and harmonic weight is counterpointed against an air of improvisational freedom – sounds liberated, rather than held to account, by Berg’s notational overkill.